718 Plus alloy is precipitated and hardened nickel-based high-temperature alloy which has excellent high-temperature performance and good processability. Such alloy gives consideration to high-temperature performance and thermal stability of Waspaloy and the excellent processability of 718 alloy during design.
It is preferred material for high-quality rotating parts of jet engines. The alloy using temperature of the 718 Plus alloy is increased by 100° F. (55°) in comparison with the 718 alloy, and the 718 Plus alloy has higher strength, more excellent formability, better wear resistance and reduced weld cracking tendency in comparison with Waspaloy or other nickel-based high-temperature alloy with higher temperature.
Compared with the 718 alloy, the range of forging temperature of the 718 Plus alloy becomes narrower, thereby being more liable to producing weld cracks; and the final one-time forging uses the temperature of 1800° F.-1900° F. (982° C.-1038° C.) to forge according to the requirements of parts. If the low forging temperature is selected, the cracks on the surface of the material are serious, and if the temperature is high, the grain size is relatively coarse, so that the performances of the structure can not meet the using requirements.
Thus, the key for mass application of the alloy is to forge the 718 Plus alloy with good surface quality and the grain size of level 6 or above in the required range of forging temperature.
By using the existing forging forming method for treatment of the 718 Plus alloy (718 Plus), there are the following disadvantages:
The 718 Plus is liable to cracking in the forging process, and more allowance is thus required to ensure the removal of the surface cracks; and when cracking is serious, the scrappage of a product is caused;
In order to ensure the surface quality of the product, relatively high ring rolling temperature needs to be used, resulting in the situation that the grain size of the product after forming is liable to being unqualified;
When the product is forging, the requirements on forging equipment and the layout of a heating furnace are high.